Stacking devices for this purpose are known and generally consist of a receiving station for successively receiving the articles with lifting means located below the receiving station to raise the articles to a stacking station. These stacking stations include catching means to catch and hold the articles in the stacking station. Typically, the receiving station will have a plurality of lifting devices arranged in parallel and means for advancing a continuous stream of articles into the receiving station. In this way, a plurality of stacks can be assembled simultaneously. These stacking station includes catching means so that when the lifting devices are retracted downwardly, the raised article engages the catchers and is thereby supported in the stacking station. When a predetermined number of articles are assembled in the stack, the stack is removed from the stacking station to enable a fresh stack to be assembled.
Each stacking station includes at least two catchers, which are arranged to engage on opposite sides of the article. Particular articles may require more than two catchers. A known form of catcher consists of a stainless steel resilient finger or plate which is arranged to be biased into the path of a tray as it is lifted so that the tray displaces the finger on its upward path and then when the tray is past the finger, the finger springs back into its normal position in the path of the tray so that when the lifter is lowered the tray is retained by the fingers in the stacking station. This arrangement is generally effective but has the disadvantage that the finger must be relatively thin to provide the necessary slight resilience but without being stiff enough to damage the tray as it passes. The finger inevitably has a sharp edge which engages the tray and which can cause damage to the trays. Also engagement of the trays is not entirely reliable. This design has the further disadvantage that the resilient fingers can break relatively easily, causing damage to the machine and, subsequently, a great deal of downtime while the machine is repaired. Furthermore, the stainless steel fingers have to be secured to the frame by screws or rivets which makes assembly of the machine quite expensive and repairs time-consuming.
Another type of catcher which addresses these problems is disclosed in GB Patent 2,394,466 B. The type of catcher disclosed in this specification has an elongate catcher element formed of a resilient plastics material which is secured to the stacking station framework by resilient plugs. Although this is an improvement on the stainless steel fingers, it does have the drawback that the catches can be dislodged in the framework when the plugs wear out or become fatigued, which again can cause damage to the articles, necessitating downtime and repair of the machine. Since the entire catcher lies in the path of the articles, damage can occur to the articles.
The present invention seeks to provide a solution to these problems.